Abstract: Natural exposure tests and accelerated natural exposure tests by spraying 3.1wt% NaCl solution were carried out on Q235 steel in Haikou atmospheric environment for 180 d. The effect of acceleration conditions on the initial corrosion behavior of the steel was studied by comparing the corrosion morphology, corrosion depth and tensile properties after corrosion. The results show that the corrosion rate of the test steel facing upward the ground was higher than facing toward the ground. Spraying NaCl solution had a significant acceleration effect on corrosion. With the extension of time, the corrosion rate of the test steel decreased due to the improvement of the protective effect of the rust layer on the matrix, and the protective effect of the rust layer formed under the accelerated natural exposure condition was stronger. The tensile properties of the test steel under both conditions decreased with the increase of corrosion mass loss rate, and under natural exposure and accelerated natural exposure conditions, the elastic modulus and percentage elongation after fracture were the most reduced, respectively. The weakening effect of corrosion on the tensile properties under natural exposure condition was higher than that under accelerated natural exposure condition, and the difference of weakening effect on elastic modulus was up to 14 times.